Anionic polymerization of conjugated dienes with lithium initiators, such as sec-butyllithium, and hydrogenation of residual unsaturation has been described in many references. The capping of mono-initiated and di-initiated living anionic polymers to form functional end groups is described in U.S. patent application Ser. No. 938,917 filed Aug. 31, 1992 (T3229).
Anionic polymerization using protected functional initiators having the structure R.sup.1 R.sup.2 R.sup.3 Si--O--A+--Li is described in U.S. Pat. No. 5,331,058 wherein R.sup.1, R.sup.2, and R.sup.3 are preferably alkyl, alkoxy, aryl, or alkaryl groups having from 1 to 10 carbon atoms, and A' is preferably a branched or straight chain bridging group having at least 2 carbon atoms. Polymerization with such a protected functional initiator, followed by capping to produce a second terminal functional group, produces difunctional polymers which sometimes can be prepared by capping polymers prepared with difunctional initiators such as 1,4 dilithiobutane and lithium naphthalide. Moreover, the use of a protected functional initiator permits formation of heterofunctional polymers having at least two different terminal functional groups on each difunctional molecule.
A preferred way to prepare difunctional polymers is to use a protected functional initiator having the structure: ##STR1## wherein A" is cyclohexyl or --CR'R"--, wherein R' is a linear alkyl having from 1 to 10 carbon atoms and R" is hydrogen or a linear alkyl having from 1 to 10 carbon atoms. The compounds of structure (A) initiate polymerization of conjugated monomers at moderate polymerization temperatures. The protected functional group survives hydrogenation of conjugated diene polymers and is readily removed by hydrolysis in the presence of methanesulfonic acid. The initiators of structure (A) can be used to make telechelic polymers by capping with ethylene oxide or oxetane.
A recent publication by J. M. DeSimone et al, Macromolecules, 26, 4854, 1993, describes the preparation of butadiene polymers capped with a perfluoroalkylchlorosilane identified as 1H,1H,2H,2H-perfluorooctyldimethylchlorosilane which gives high capping efficiency. This paper describes the expected improvement in surface properties that can be achieved by blending this material with conventional polymers.